You may have seen the studies linking endurance exercise to heart problems. But are they the real deal?

Anyone who’s ever watched a marathon can agree on one thing: Distance runners are in really, really good shape. So when we saw research asserting that endurance exercise is actually bad for your health, we were shockedâ€”and skeptical.

AÂ Wall Street JournalÂ article about this growing body of anti-endurance exercise thinking cites studies that say that extreme exercise puts athletes at a higher risk for coronary-artery plaque, irregular heart beats, heart disease, and heart attacks, among other things. TheÂ WSJÂ even went so far as to title its piece “The Exercise Equivalent of a Cheeseburger?,” though it did also note that many sports scientists disagree with or put forth qualifications about the research.Â But how could endurance exercise, long considered the gold standard of fitness, be bad for your heart? The article quotes John Mandrola, a cardiac electrophysiologist:

“Heart disease comes from inflammation and if you’re constantly, chronically inflaming yourself, never letting your body heal, why wouldn’t there be a relationship between over exercise and heart disease?” said John Mandrola, a cardiac electrophysiologist and columnist for TheHeart.org.

Still, we weren’t totally convinced, so we went to Dr. Daniel Forman, the medical director of the Exercise Testing Laboratory and cardiac rehabilitation at Brigham and Women’s Hospital, for some answers.

Is there validity to the idea that endurance exercise is bad for your heart?

If you’re doing intense exercise for many hours a day, multiple days a week, there are data that suggest that in some people, it may be associated with detrimental aspects. But if you say endurance exercise, for the vast majority of people the intensities are much lower. They do not achieve the kind of several hour, consecutive exercise seven days a week that I’m describing. It’s several days a week, they slow down when they’re tired, then they speed up, and that’s really very different.

What kind of damage could people experience?

It’s really the fringes, the extremes, which maybe, in some peopleâ€”not in everyone, but in some peopleâ€”there could be an overuse component where you have aspects of right heart damage: overly burdensome strain on the right heart â€¦ with increased fibrosis and ultimately greater susceptibility to arrhythmia and heart failure. But that really is a small fraction of the percent of the very small percent of people that come close to exercising [with that intensity].

So this isn’t a reason to stop exercising?

I would guesstimate that there are several thousand articles that all show consistent benefits of exercise, and then there’s one or two that show a subset ofâ€”it’s really triathlon people or people that run 100 miles consecutively, really the super, super intense athletesâ€”maybe in some cases have some bad aspects, and people rivet on those. It’s almost as a justification: “I told you I shouldn’t exercise!” That’s a distortion, because everyone who exercises on a more achievable level benefits. This is really not you; this is people who run triathlons 10 times a year that are just obsessed with their athleticism, and that’s not the average patient or the average individual. I hope everyone else continues to exercise.